Extraction of metals & reduction

Figure 11 shows part of the reactivity series of metals.

The method used to extract a metal from its ore is related to the metal’s position in the reactivity series.

Which metal is found in the Earth’s crust as an uncombined element?

Name one metal in Figure 11 that is normally extracted by electrolysis.

25 000 kg of an ore of iron was found to contain 10 050 kg of iron.

Calculate the percentage of iron in this ore of iron.

percentage of iron in ore =_........

When copper oxide is heated with carbon, the products are copper and carbon dioxide.

Write the word equation for this reaction.

In this reaction, copper oxide loses oxygen.

State the type of reaction when copper oxide loses oxygen.

In one reaction, 159.0 g of copper oxide was heated with excess carbon to produce 127.0 g of copper.

Use this information to calculate the mass of copper formed, in g, when 238.5 g of copper oxide is reacted with excess carbon.

mass of copper =_........ g

State why this reaction with copper oxide uses excess carbon.

A solution of zinc sulfate was made by dissolving 23.8 g of the compound in water and was made up to a total volume of 250 cm³ with water.

Calculate the concentration of this solution in g dm^–3.

Give your answer to 2 significant figures.

concentration =_........ g dm^–3

Malachite, Cu₂CO₃(OH)₂, is a mineral containing copper.

When heated, malachite decomposes to form copper oxide, carbon dioxide and water.

Which apparatus should be used to heat the malachite and test for carbon dioxide?

When carbon dioxide is bubbled through limewater, a precipitate forms. This precipitate solid makes the limewater cloudy.

Name the precipitate that makes the limewater cloudy.

The equation for the decomposition of malachite when it is heated is

Calculate the maximum mass of copper oxide that can be formed when 22.1 g of malachite is decomposed completely.

(relative atomic masses: Cu = 63.5, O = 16.0, C = 12.0, H = 1.0)

maximum mass of CuO =_........

Copper can be extracted from copper oxide by heating the copper oxide with carbon.

A student investigated two methods to extract the maximum mass of copper from copper oxide.

Figure 3 shows the two methods.

Comment on the strengths and weaknesses of these two methods.

This question is about the extraction of metals.

Give two advantages of obtaining metals by recycling rather than by extracting them from their metal ores.

Small amounts of some metals are extracted using displacement reactions.

In one process, zinc dust is used to precipitate cadmium metal from a solution containing cadmium ions.

cadmium ions cadmium

Explain why this displacement reaction can be described as a redox reaction.

The formula of the cadmium ion is Cd²⁺. The formula of the phosphate ion is PO₄^3–.

Which is the formula of cadmium phosphate?

One of the alternative biological methods of extracting metals from very low‑grade ores is bioleaching using bacteria.

Give one disadvantage of this method of extracting metals from low‑grade ores.

Lead is low in the reactivity series.

Describe how to obtain a sample of lead from some lead oxide in the laboratory.

Figure 13 shows part of the reactivity series of metals.

Which metal reacts when added to cold water?

A student investigates the reactivity of four different metals.

The student adds an equal‑sized piece of each metal to separate test tubes containing dilute hydrochloric acid.

The student’s observations for zinc and copper are recorded in Figure 14.

Use the information in Figure 13 and in Figure 14 to predict the observations for the reactions of magnesium and of iron with dilute hydrochloric acid.

magnesium

iron

When metals react with acids, hydrogen gas is produced.

Describe the test to show that the gas is hydrogen.

When magnesium reacts with hydrochloric acid, magnesium chloride and hydrogen are formed.

Complete the balanced equation for the reaction.

*(c) There are three common methods of obtaining metals from the Earth’s crust:

• mine the pure metal

• mine the metal ore and heat it with carbon

• mine the metal ore and electrolyse the molten compound.

The method used to obtain a metal is linked to its position in the reactivity series of metals.

Aluminium, gold, iron, and silver are some commonly used metals.

Use the reactivity series in Figure 13 to state and explain the method chosen to obtain each of these four metals.

The method used to extract a metal from its ore depends on the position of the metal in the reactivity series.

Aluminium is extracted from its ore by electrolysis.

Explain why this method is used to extract aluminium from its ore.

One step in the extraction of titanium metal involves the displacement reaction between titanium chloride, TiCl₄, and magnesium.

This equation can be simplified as

Explain why this displacement reaction can be described as a redox reaction.

The formula of the sulfate ion is SO²⁻₄.

Which of the following is the formula of titanium sulfate containing the Ti⁴⁺ ion?

Phytoextraction is an alternative biological method that can be used to extract metals from very low-grade ores.

Give one disadvantage of phytoextraction as a method of extraction of metals.

Copper is low down in the reactivity series and can be obtained from copper oxide.

Devise a simple method to obtain a sample of copper from copper oxide in the laboratory.

When chromium reacts with oxygen, chromium oxide is formed.

Write the word equation for this reaction.

What type of reaction occurs when chromium reacts with oxygen?

Calculate the relative formula mass of chromium oxide, Cr₂O₃.

(relative atomic masses: O = 16, Cr = 52)

relative formula mass =_........

Three different metals are added to separate test tubes of acid.

The observations are shown in Figure 4.

Place the metals in order of reactivity from most to least reactive.

Hydrogen is given off when magnesium reacts with acid. The hydrogen is tested by collecting the gas in a test tube and igniting it.

What is the safest way to ignite the gas?

State the observation made in this test that shows that the gas is hydrogen.

Iron is extracted by heating iron oxide with carbon. Electrolysis of molten iron oxide is not used to extract iron.

State why iron can be extracted by heating iron oxide with carbon.

State why electrolysis is not used to extract iron.

The order of reactivity of copper, magnesium and zinc can be determined by the displacement reactions between these metals and solutions of their salts.

You are provided with

• samples of the three metals

• solutions of copper sulfate, magnesium sulfate and zinc sulfate.

Describe the experiments that can be done to determine the order of reactivity of these metals by displacement reactions.

Metals can be extracted from ores found in the Earth’s crust.

Explain why aluminium cannot be extracted from its ore by heating with carbon but can be extracted by electrolysis.

Titanium is extracted from its ore in several stages.

In the first stage, titanium chloride is formed as a gas.

The gas is cooled to form liquid titanium chloride containing dissolved impurities.

Suggest how pure titanium chloride could be separated from the impurities.

In another stage, the pure titanium chloride, TiCl₄, is reacted with 500 moles of magnesium, an excess.

Calculate the number of moles in 45 000 grams of titanium chloride.

(relative atomic masses: C l = 35.5, Ti = 48.0)

number of moles titanium chloride =_........

Show that the 500 moles of magnesium added is an excess.

After this reaction, there is a mixture of the solids magnesium, titanium and magnesium chloride.

Titanium does not react with dilute hydrochloric acid.

Suggest a simple method to separate titanium from the mixture.

Some metals are found in the Earth’s crust as uncombined elements. Reactive metals are found in ores.

In ores, metals are combined with other elements.

Which of these metals is found as the uncombined element in the Earth’s crust?

Give two advantages of recycling metals rather than extracting metals from their ores.

An ore of iron is mostly iron oxide, Fe₂O₃. Iron can be extracted from this iron oxide by heating it with carbon.

Balance this equation for the reaction that takes place.

Most copper ores are described as low grade. This means that the percentage of copper in the ore is very small.

5000 kg of one copper ore was found to contain 42.5 kg of copper.

Calculate the percentage of copper in this ore.

percentage of copper in ore =_........

In one stage of the extraction of lead from its ore, lead oxide is heated strongly with carbon.

The equation for the reaction is

Explain, using this equation, which substance has been oxidised in this reaction.

A titanium ore was analysed and found to contain 12 g of titanium atoms combined with 8.0 g of oxygen atoms.

Calculate the empirical formula of this titanium compound. (relative atomic masses: Ti = 48, O = 16)

You must show your working.

empirical formula =_........

(a) One way to extract metals from land contaminated with metal compounds is phytoextraction. When plants grow they absorb metal ions through their roots. The plants are harvested, dried and burned forming an ash. The ash contains metal compounds.

Plants were grown in a piece of ground contaminated with nickel compounds.

1 kg of the ash from these plants contained 142.0 g of nickel compounds.

Calculate the percentage by mass of nickel compounds in the ash.

Nickel is extracted from nickel compounds.

State an advantage of extracting nickel by phytoextraction rather than from its ore.

Some nickel ores contain nickel sulfide.

In the first stage of extracting nickel from nickel sulfide, the nickel sulfide, NiS, is heated in air to form nickel oxide, NiO, and sulfur dioxide.

Write the balanced equation for this reaction.

In the final stage of the extraction process, a nickel compound is electrolysed to produce pure nickel.

An advantage of producing a metal by electrolysis is that

In a different method of obtaining nickel, the process produces a mixture of the liquids nickel tetracarbonyl and iron pentacarbonyl.

The boiling point of nickel tetracarbonyl is 43 °C. The boiling point of iron pentacarbonyl is 103 °C. These two liquids mix together completely.

Describe the process used to separate these two liquids.

Most metals are extracted from ores found in the Earth’s crust.

The method used to extract a metal from its ore is linked to the reactivity of the metal.

Part of the reactivity series is shown in Figure 14.

Iron ore contains iron oxide.

Iron is extracted from iron oxide by heating the oxide with carbon.

iron carbon

In this reaction

The formula of the iron oxide is Fe₂O₃.

Calculate the maximum mass of iron that can be obtained from 240 tonnes of iron oxide, Fe₂O₃.

(relative atomic masses: O = 16, Fe = 56)

mass of iron =_........ tonnes

Aluminium cannot be extracted by heating its oxide with carbon. Aluminium has to be extracted from its oxide by electrolysis.

Explain why.

Predict the method that will have to be used to extract calcium from its ore.

*(d) Aluminium is extracted from its ore by electrolysis. Iron is extracted from its ore by heating with carbon. Both metals can also be obtained by recycling.

Explain the advantages of recycling aluminium and iron rather than extracting them from their ores.

Most metals are extracted from ores found in the Earth’s crust.

The method used to extract a metal from its ore is linked to the reactivity of the metal.

Part of the reactivity series is shown in Figure 2.

Iron ore contains iron oxide.

Iron is extracted from iron oxide by heating the oxide with carbon.

iron carbon

In this reaction

The formula of the iron oxide is Fe₂O₃.

Calculate the maximum mass of iron that can be obtained from 240 tonnes of iron oxide, Fe₂O₃.

(relative atomic masses: O = 16, Fe = 56)

mass of iron =_........ tonnes

Aluminium cannot be extracted by heating its oxide with carbon. Aluminium has to be extracted from its oxide by electrolysis.

Explain why.

Predict the method that will have to be used to extract calcium from its ore.

In recent years, researchers have been investigating alternative methods of extracting metals from soils.

Researchers have found that growing certain plants in appropriate areas can result in the phytoextraction of copper.

Describe how growing plants can result in the phytoextraction of copper.